Preparation of hydroxy aromatic carboxylic acids



Patented Nov. 2, 1948 v PREPARATION OF HYDROXY AROMATIQ Q ,j CARBOXYLIC ACIDS Enno Wolthuis, Cranford, and Henry M. Shafer,

Westfleld, N. J., assignors to General Aniline & Film Corporation, New York, N. Y., a corporation of Delaware No Drawing.

The present invention relates to the production of hydroxy aromatic carboxylic acid compounds. More particularly, the invention relates to the production of such compounds by the carboxylation with carbon dioxide of a potassium salt of a phenol suspended in a halogenated benzene as a diluent. 1

The production of hydroxy aromatic car-boxylic acids is generally carried out by the so-called Kolbe synthesis which involves carboxylating alkali metal salts of phenols. Industrially, the process essentially consists in subjecting the'dry alkali metal phenolates in the absence of any liquid diluents to carbon dioxide under pressure. However, this procedure requires special equipment and the phenolate is often formed as lumps rather than as a finely divided powder. It is more difiicult to completely dry the phenolate so produced, and. there is a tendency to local overheating and decomposition. To overcome the drawbacks of the dry" method of carboxylation,

it hasbeen proposed to carry out the reaction in the presence of various solventsor diluents, such as water, naphthalene, paraiiin, dioxane, pyridine, fi-naphthol, and various phenols. However, the use of the heretofore proposed solvents introduces other drawbacks. Some cause side reactions, are corrosive on the reaction vessels, or

k 'are toxic. Others are aiiected by,the carbon dioxide or are inflammable. Still others, like parafiln, have the disadvantage of limiting the temperature range for carboxylation by the melting pointof the diluent, and are more difllcultto remove from the reaction product.

According to our invention, we overcome these drawbacks and at the same time improve the yields of the reaction product by carrying out the r any difficulty in obtaining a dry phenolate for carboxylation. Other advantages are that it is relatively non-inflammable and non-toxic.

By use of the potassium salt-of .a phenol in combination with o-dichlorobenzene we have Application November 15, 1945,v Serial No. 628,986

' 14'Claims. (01. 260-315) found that the yields of the hydroxy carboxylic acids are greater than in the case of using the sodium salts of the phenols. We have also found in the carboxylation of those phenolates where variety of phenols that may be readily converted two isomeric acids may be formed, such as in the case of fi-naphthol, Z-hydroxy carbazole, and- Z-hydroxy diphenylene oxide, that the principal product of the reaction is the 2-hydroxy a-carboxylic acid isomer-when there is used the potassium salt'of these phenols with o-dichlorobenzene ,as the diluent, and that the formation of the 2-hydroxy-1-carboxyiic acid isomer is suppressed. Since the 2.3 isomer is the generally desired isomer because oi? its great usefulness in theproduction of couplers-for forming azo dyes, our process has this additional advantage which is not obtained when using the sodium salt.

Another additional feature of our invention is that what 2.1 isomer is present in the reaction an additional feature oi? our invention that theyield and purity of the 2.3 isomer can be further increased by salting out the reaction product with potassium carbonate.

By the use of the potassium salts of phenols and o-dichlorobenzene in accordance with our invention, hydroxy carboxylic acids can readily be obtained from a wide variety of phenols in good yields and high purity. As examples of the great by our process into the corresponding hydroxy carboxylic acids may be mentioned 2-hydroxy diphenylene oxide, 2-hydroxy carbazole, 2-hydroxy u-benzocarbazole, B-hydroxy quinoline, fi-amino-l-naphthol, 10-hydroxy-7,8-benzoquinoline, o-naphthol, a-naphthol, phenol, and the like.

According to our invention, the preformed potassium salt of the phenols may be utilized. However, according to a preferred modification of our invention, the potassium phenolate is produced anddehydrated in the o-dichlorobenzene, which is then utilized as the reaction mixture on which is carried out the carboxylation treatment. To form the potassium phenolate, the phenol selected is reacted with at least an equivalent amount of potassium hydroxide in the presence of the diluent. The water formed by the formation of the salt is then removed, a convenient way potassium phenolate suspended in o-dichlorobenzene is then subjected to carboxylatlon with carbon dioxide. The dichlorobenzene may be removed from the reaction product resulting from the carboxylation byany suitable method. Steam distillation is highly suitable for this purpose. Any residues may be removed by filtration. The

filtrate may then be acidified with any suitable acid, as for example. hydrochloric acid, where it is desired to convert the salt of the acid to the hydroxy carboxylic acid.

Where the phenol utilized forms 2-hydroxy-3- carboxylic acid and 2-hydroxy-1-carboxylic isomers, the isomers are readily separated by salting out the 2.3 isomer, the potassium salt of which is less soluble than the 2.1 isomer. by adding potassium carbonate tothe reaction mass obtained after completion of the carboxylation operation.

The conditions for carrying out the reactions may be varied within wide limits. The optimum conditions will vary somewhat for each particular phenol.' In forming the potassium salts, it is preferable to use at least one equivalent amount of potassium hydroxide for each equivalent amount of the phenol. Any suitable temperature may be utilized in the reaction to form the salt. In general, a range of about 100-150 C. is preferable. In drying by distillation, it has'been found to be highly desirable to remove only so much of I low and the products obtained are found to be of low purity. The temperature may. in general, range from 20 C. to approximately 210 0., al-

though a preferred range is .Irom'about 150 C. to

about 200 C. The pressures at which the reaction is carried out may extend up to about 250 pounds per square inch. However. a preferred range is from about -120 pounds per square inch.

Where phenols are utilized which produce two isomeric acids, such as 2-hydroxy-3-carboxy and 2-hydroxy-1-carboxy isomers, the separation of the isomers is based upon the difference of solubility of their potassium salts. We have found that the 2.3 isomer is less solublethan the 2.1 isomer and can be readily salted out by addition of potassiumcarbonate to the reaction mass after completion or the carboxylation. By utilizing large amounts of potassium carbonate, it is possible to increase the yield of the 2.3 isomer isolated. The mother liquid, after salting out, might contain a small quantity 0! both isomeric acids. when a suificient amount of the motherliquid givenby way of illustration and not by way of limitation.

Example 1 V An iron autoclave, fitted with a stirrer, thermometer, gas inlet. and distillation outlet ischarged with 45.8 parts of 2-hydroxycarbazole. 650 parts of -o-dichlorobenzene and 16.8 parts of potassium hydroxide. The mass is heated to 120 C. and held at 120-130 C. until the potassium salt is completely formed. About one-half of the dichlorobenzene is removed, together with all the water present by vacuum distillation at 120-140 C. The mass is then heated to 150 C. and carbon dioxide is charged in periodically until the pressure reaches about pounds per square inch. Heating is continued at 150 C., while maintaining the pressure at 60-63 pounds until the carboxylation is complete. The mass is cooled to 100 C., the pressure released, and the dichlorobenzene removed by steam distillation The residue is diluted to 800 parts with water heated .to 80 C. and sufficient acid, such as sulfuric.

added to precipitate any unreacted 2-hydroxy carbazole which is then removed by filtration.

The filtrate is heated to 80 C. End 100 parts of potassium carbonate are added as a salting out agent, and the mass heated at 80-90 C. until solution is efiected. The solution is cooled rapidly to 20 C. and stirred to complete precipitation. The potassium salt of 2-hydroxycarbazole-3-carboxylic acid which precipitates is filtered and sucked dry. The cake is washed with 100 parts of 10% potassium carbonate solution. The filtrate and wash contain all of the potassium salt of Z-hydmxycarbazole-l-carboxylic acid isomer and only a small amount of the 2.3 isomer.

The potassium salt (filter cake); is sludged in I 2000 parts of water and heated to 80 C. -It isthen acidified to Congo paper with HCl, heated to 90 C., and filtered. The 2-hydroxycarbazole-3- carboxylic acid is washed neutral with hot 1 (50 C.) water and dried. The yield is 46.6-48.2

parts or 82-85% of theory. It can be readily converted into an aryllde suitableas a coupler to form azo dyes.

Example 2 An iron autoclave fitted with an agitator, ther-,

mometer, gas inlet, and distillation outlet, is charged with 46 parts of 2-hydroxydiphenylene oxide, 14.0 parts of potassium hydroxide. and 600 parts of o-dichlorobenzene. The mass is heated to 100 C. and held at l00-110 C. with stirring, to form the potassium salt. About one-half of the dichlorobenzene and aliof the water is distilled of! under vacuum at l20-140 C. Dry carbon dioxide is charged into the mass at 155-165 C. and up to pounds pressure. The temperature is gradually raised to 200 C. and held at has been accumulated, these may be rear'ily isoillustrate various 200-206 C. and at a pressure of 70-77 pounds until carboxylation is complete. The mass is cooled; the pressure is released; about 500 parts of water are. added; and the dichlorobenzene is steam distilled ofl. The residual solution is filtered at C. to remove any residues. 25 parts of potassium carbonate are added to the filtrate with stirring, cooled to 10 0., and filtered. The

2 hydroxydiphenylene oxide 3 carboxylic acid is salted out while the 2-hydroxy diphenylene oxide-l-carboxylic acid is in the filtrate.

The filter cake is dissolved in 2000 parts or water at -95 0. Some of the color is removed with about 10 parts of charcoal, filtered, and the 2-hydroxydiphenylene oxide-3-carboxylic acid is precipitated with hydrochloric acid. It is fii '5 tered, washed neutral, and dried at 70-75 C. The yield is approximately 65% of theory.

Example 3 The process of Example 2 is repeated, the carboxylation procedure, however, being carried out at about 120 pounds carbon dioxide pressure and 200 C. The yield of the 2.3 isomer is approximately 75%.

' Example '4 Aniron autoclave is charged with 19.6 parts of 3'-hydroxy-7,8-benzocarbazole,. 5.3 parts of potassium hydroxide and 600 parts of o-dlchloropressure is reached. A temperature rise of from 8 to 10 C. occurs at this point.

The temperature is allowed to fall to 150 C. and carbon dioxide is added while maintaining a pressure of 250 pounds. After no further pressure drop is noted over a period of 15 minutes, the autoclave is heated at 195-200 C. for nine hours.

The dichlorobenzene is removed by steam distillation and any residues removed by filtering. On reducing the pH to 8-8.2 with HCl about 2.5 parts of unchanged hydroxybenzocarbazole separates' from the solution at 90-100 C. and is illtered off. On acidifying the filtrate, the 3'-hydroxy-7,8-benzocarbazole-2'-carboxylic acid separates out. The mass is filtered at 25 C., and washed with hot water until neutral. The yield is 12.8-13.9 parts.

Example An autoclave is charged with 40 parts of 5- amino-l-naphthol; 15.6 parts potassium hydroxide, 25 parts water, 500 parts o-dichlorobenzene, and 2 parts oi a wetting agent such as isobutyl naphthalene sodium suli'onate.

With vigorous agitation the mixture is heated at 115-120 C. until the formation of the potassium salt is complete. Suspension of the salt in the o-dichlorobenzene is facilitated by the wetting agent. Vacuum is then applied and about 200 parts o-dlchlorobenzene is distilled oil to-' gether with the water. The temperature is then raised to 150 C. and carbon dioxide is injected up to about 75 pounds per square inch. The temperature is raised further to 175 C. and maintained until the carboxylation reaction is completed. .The reaction mass is then cooled to about 100 C. and the pressure is released. About 1400 parts of water are then added and the o-dichlorobenzene removed by steam distillation. Carbon dioxide is then introduced to adjust the acidity to a pH of 7-8. The precipitated impurities are filtered off. The product. 5-amino-1-hydroxy-2- naphthoic acid, is isolated in good yield from the filtrate by the addition of hydrochloric acid.

Since the potassium salts of the phenols are not appreciably soluble in the halogenated benzene compounds utilized as diluents, it would ordinarily be expected that good yields of the hydroxy carboxylic acids would not be obtained and that the reaction would not proceed smoothly. Contrary to what would be expected, our invention results in the unexpected and important advantages of comprises subjecting the potassium phenolate thereof suspended in a. halogenated benzene to reaction with carbon dioxide.

2. A process of carboxylating a phenol which comprises subjecting the potassium phenolate thereof suspended in a halogenated benzene to. reaction with carbon dioxide at an elevated temperature up to about 210 C. and under a superatmospheric pressure up to about 250 pounds per square inch. 3. A process of carboxylating a phenol which comprises subjecting the potassium phenolate thereof suspended in o-dichlorobenzene to reaction with carbon dioxide. at a temperature between about 150 andi200 C. and under a presisurlel of from about to 120 pounds per square 4. A process of carboxylating a phenol which comprises subjecting the potassium phenolate thereof suspended in a halogenated benzene in the proportion of 1 part to at least 5 parts of the latter to reaction with carbon dioxide.

5. A process of carboxylating a phenol which comprises subjecting the potassium phenolatethereof suspended in o-dichlorobenzene in the proportion of 1 part to at least 5 parts: of the latter to reaction with carbon dioxide.

6. A process of carboxylating a phenol which oomprises converting the phenol to the phenolate by reaction with potassium hydroxide in a halogenated benzene as diluent, drying the mixture by distillation while retaining therein sufilcient of the diluent to provide a suspenson of 1 part of the potassium phenolate to at least 5 parts of the diluent and reacting the dry suspension of the phenolate with carbon dioxide, the diluent being present initially in amount suflicient to provide the combined requirements of the distillationstep and of the dry suspension of the phenoto reaction with carbon dioxide at a temperature good yields, high purity of product, ease of sepfrom about to 200 C. and under a pressure of about 250 pounds per square inch.

10. A process of preparing 2-hydroxydiphenyleneoxide-3-carboxylic acid which comprises subjecting the potassium salt of 2-hydroxydiphenyleneoxide suspended in o-dichlorobenzene to contact with carbon dioxide at an initial temperature of about C.,gradually increasing the temperature of the mixture, and conducting the reaction at temperatures within the rangeof about 155 to 206 C. and under pressures within the 12. The process of claim 11, wherein the iso meric mixture consists of the potassium salts caror the 2.1 and 2,8-hydroxycarbazoie carboxylie acids;

13. The process of claim 11, wherein the iso= meric mixture consists oi the potassium salts of the 2,1 and 2,3-hydroxydiphenyleneoxide car boxylic acids.

by salting out with potassium carbonate.

' ENNO WOLTHUIS.

HENRY M. SHAFER.

8 nnrnaaucas crrrazn The following references are oi record in the tile of this patent:

UNITED STATES PATENTS Number Name Date 1,503,984 Cone Aug. 5, 1924 1,648,839 Calcott Nov. 8, 1927 1,819,127 Bchmelzer Aug. 18, 1931 2,050,958 Muth Aug. 11, 1936 2,132,356 Lecher Oct. 4, 1938 2,182,857 Lecher Oct. 4, 1938 2,161,524 Morschel June 8, 1939 2,193,336 Lecher Mar. 12, 1940 FOREIGN PATENTS Number Country Date 598,506 Germany Mar. 1, 1934 

